Geometry and UV-Vis Spectra of Au3+ Complexes with Hydrazones Derived from Pyridoxal 5′-Phosphate: A DFT Study

Abstract

Gold(III) complexes with different ligands can provide researchers with a measure against pathogenic microorganisms with antibiotic resistance. We reported in our previous paper that the UV-Vis spectra of different protonated species of complexes formed by gold(III) and five hydrazones derived from pyridoxal 5′-phosphate are similar to each other and to the spectra of free protonated hydrazones. The present paper focuses on the reasons of the noted similarity in electron absorption spectra. The geometry of different protonated species of complexes of gold(III) and hydrazones (15 structures in total) was optimized using the density functional theory (DFT). The coordination polyhedron of gold(III) bond critical points were further studied to identify the symmetry of the gold coordination sphere and the type of interactions that hold the complex together. The UV-Vis spectra were calculated using TD DFT methods. The molecular orbitals were analyzed to interpret the calculated spectra.

Complexes of Gold(III) with Hydrazones Derived from Pyridoxal: Stability, Structure, and Nature of UV-Vis Spectra

“…Second, the calculated UV-Vis spectrum of the single protonated complexes of gold(III) with hydrazones has shown the worst agreement with the experimental spectra [40]. What is the reason behind this discrepancy?…”

“…Our previous papers [39,40] were devoted to the study of the stability and structure of several gold(III) complexes with hydrazones derived from pyridoxal 5′-phosphate. PLP-derived hydrazones have received less attention with regard to their biological activity than PL hydrazones.…”

“…Our previous papers [39,40] were devoted to the study of the stability and structure of several gold(III) complexes with hydrazones derived from pyridoxal 5 ′ -phosphate. However, some questions remained unanswered.…”

“…First, is the phosphate group involved in the complex formation? Can the partial negative charge accumulated on the phosphate group make it attractive for the cations (including gold(III) species) [40]? This possibility cannot be neglected, as both insoluble [41] and soluble [42] complexes of gold(III) with inorganic phosphate are known, including a valuable histochemical label, so-called black-gold [43][44][45].…”

Evaluation of novel pyridoxal isonicotinoyl hydrazone (PIH) derivatives as potential anti‐tuberculosis agents: An in silico investigation

“…Morcoss et al [55] found promising anti‐cancer activity in benzimidazole‐hydrazone derivatives, while Erol et al [56] demonstrated good anti‐microbial activity against E. faecalis. Sajjan et al [57] explored parameters against anti‐cancer studies, and Pimenov et al [58] studied gold (III) condensation with hydrazones. Uddin et al [59] investigated the anti‐cancer properties of benzylidinemalononitrile and ethyl 2‐cyano‐3‐phenylacrylate derivatives using comprehensive in silico studies.…”